This invention relates to novel perfluoroalkyl-substituted amino acid derivatives and their use in water dispersible polymeric foam stabilizers for aqueous, alcohol-resistant, polar fire fighting foam formulations (AR-AFFF), and for textile and paper oil-proofing finishes. More particularly it relates to oligomers or copolymers of an aliphatic diamino acid with 3 to 10 carbon atoms such as lysine with a chain extender and having at least two perfluoroalkyl groups attached to nitrogen atoms.
Aqueous Fire-Fighting Foam (AFFF) formulations contain water-soluble fluorosurfactants along with hydrocarbon surfactants. They are effective in extinguishing non-polar solvent fires. When an AFFF formulation comes in contact with a burning hydrocarbon fuel, the water, which contains both fluoro- and hydrocarbon surfactants, drains from the foam and forms a thin film on top of the burning fuel. This film does not sink, but due to its low surface energy ( less than 18 dynes/cm, which is lower than that of heptane), it spontaneously spreads across the surface of the burning fuel. There it acts as a vapor suppressant and, in combination with the aqueous foam, extinguishes the fire and prevents reigniton of the fuel. It is important in this application that the foam have a long foam life on the hot fuel; otherwise the fuel can reignite, an event called bumback. A long foam life which provides bumback resistance is achieved by having a foam which is xe2x80x9cwetxe2x80x9d, that is hydrated, and from which water can drain down onto the surface and replenish the seal. On a non-polar fuel like gasoline, this task is simple since water and the water-soluble surfactants are not soluble in the fuel.
This task is considerably more difficult on polar fuels like isopropanol and acetone. Besides the fluoro- and hydrocarbon surfactants found in conventional AFFF formulations, an Alcohol-Resistant (=AR) AFFF formulation contains a water-soluble but polar-solvent insoluble fluorochemicalxe2x80x94also referred to as xe2x80x9calcoholophobicxe2x80x9dxe2x80x94foam stabilizer (as described in this invention) along with a polysaccharide such as xanthan gum. When these additional materials come in contact with a burning polar fuel fire, they precipitate and give rise to a membrane which protects the foam from dissolving in the polar solvent. This membrane creates a vapor barrier which extinguishes the fire and prevents reignition of the fuel along with keeping the foam hydrated.
Polysaccharides and/or high molecular weight synthetic polymers may be used in AR-AFFF formulations without a fluorochemical foam stabilizer and provide about the same efficacy. The problem with a foam concentrate containing only polysaccharides and/or high molecular weight synthetic polymers is that its viscosity is high, and the concentrate behaves in a thixotropic manner. It is difficult to use a high viscosity foam concentrate since it is hard if not impossible to pump it through a fire nozzle. AR-AFFF formulations containing fluorochemical foam stabilizers require much lower amounts of polysaccharides and/or high molecular weight synthetic polymers, thus lowering the viscosity of the foam concentrate. Additionally, foam concentrates containing fluorochemical foam stabilizers in AR-AFFF formulations tend to behave in a Newtonian manner.
Fire fighting foam stabilizers containing at least one perfluoroalkyl group and water-solubilizing functionalities such as carboxy and amido groups are described in U.S. Pat. Nos. 4,460,480 and in 5,218,021.
French patent application 2,637,506-A describes an alcoholophobic and oleophobic fire extinguishing foam concentrate which contains a polyhydroxy-polyamine containing at least one quaternary N atom and/or a polysaccharide which is chemically bonded to highly fluorinated C4-C20alkyl groups, instead of containing the fluorosurfactant and the polysaccharide or other alcoholophobic agent separately in the concentrated mixture.
Alcoholophobic fire fighting foam stabilizers containing at least one perfluoroalkyl group along with poly-quatemary ammonium and carboxy functionalities are described in world patent applications WO 90/02110 A1 and WO 90/03966 A1 along with publications by S. Szxc3x6nyi in Fire Safety Journal, 16, pp. 353-365 (1990) and Progress in Colloid and Polymer Science, 81, 136-139 (1990).
Since quatemary ammonium groups cause incompatibility with the anionic surfactants used in fire fighting formulations, further improvements have been described in WO 94/18245. This reference teaches compounds which contain a combination of at least two perfluoroalkyl groups, amino groups other than quaternary ammonium groups, carboxylic groups and other water-solubilizing groups attached to amino groups.
S. Szxc3x6nyi, Corn. Joum. Com. Esp. Deterg., 22, pp.297-304 (1991) a refers to a commercial state-of-the-art alcoholophobic foam stabilizer, MX30, as a perfluoroalkylated polyamino acid. However, from the various Szxc3x6nyi references discussed above it appears that MX30 is a polyamine derivative with perfluoroalkyl and COOH groups attached to amino nitrogens via a linking group.
U.S. Pat. No. 4,606,973 discloses aminoethylmethacrylate-acrylic acid copolymers in which the amino groups have been reacted with perfluoroalkyl carboxylic acids.
Japanese patent application S59-230566 describes foam stabilizers useful for polar solvents which contain an anionic or amphoteric fluorosurfactant, polyethylenimine of MW 4,000 to 100,000, and a polybasic acid compound.
U.S. Pat. No. 3,769,307 claims perfluoroalkylsubstituted polyethylenimine compositions and the preparation thereof. This patent also claims the use of such compounds as textile finishes providing oleophobic properties. German Offenlegungsschrift 2 018 461 describes surface-active agents and foam stabilizers for polyurethane foams which are polyethylenimines substituted by one or more perfluoroalkyl groups, as well as perfluoroalkyl-substituted polyamines containing up to 16 carboxy or sulfonic acid groups and/or hydrophilic amide groups. Although not directed toward foam stabilizer compounds for polar solvent fire fighting foams, the composition of this patent is described as very soluble in alcohol/water mixtures, but poorly soluble in alcohol (=xe2x80x9calcoholophobicxe2x80x9d) and water itself, making it a candidate for such foam stabilizers. Indeed, the above-mentioned WO 94118245 reference describes the synthesis of a perfluoroalkyl- and carboxy-substituted polyethylenimine from tetraethylene-pentamine, a perfluoroalkyl acyl chloride and chloroacetic acid.
U.S. Pat. No. 5,750,043 also describes foam stabilizers containing polyamines wherein the amino groups are partially or completely substituted by perfluoroalkyl groups as well as hydrophilic groups, such as carboxy groups.
Effective foam stabilizers on polar solvents have to be essentially insoluble in these solvents. Most commonly used are polyamines which are N-substituted by perfluoroalkyl and carboxy groups, such as those described above. The present invention discloses a new class of poly-perfluoroalkyl- and carboxy-substituted amines in which the carboxy groups are attached to a carbon atom and which are the reaction products of oligomers or copolymers of an aliphatic diamino acid having 3 to 10 carbon atoms, such as lysine, a chain-extender such as epichlorohydrin, a dihalide or an aliphatic diepoxide, an amino-reactive allyl compound, and a perfluoroalkyl iodide.
A class of non-polymeric amphoteric compounds which contain RF-, acid and amino groups, and which are useful to impart oil repellency to paper products are di-RF-ramino acids obtained by reaction of an amino acid, allyl glycidyl ether and an RF-iodide as described in U.S. Pat. No. 5,491,261. However, these compounds are not oligomers or polymers.
It has now been discovered that by a similar synthetic route, polymeric RF-amino acids of the type which are useful as foam stabilizers for polar solvent fire-fighting foams, and which contain a plurality of RF groups as well as amino, and carboxy or other hydrophilic groups, can conveniently be prepared in similarly high yields and essentially without waste from (A) an aliphatic diamino acid having 3 to 10 carbon atoms such as lysine, (B) a chain extender such as epichlorohydrin, a dihalide or a diepoxide, (C) an amino-reactive allyl compound and (D) a perfluoroalkyl iodide, and, optionally, other reactants.
The resulting mixture of poly-perfluoroalkyl-allyl- and poly-perfluoroalkyl-iodopropyl-substituted-polyamino acids are useful as grease-proofing agents for paper, but more importantly, they have been found to act as excellent foam stabilizers for Aqueous Fire-Fighting Foam (AFFF) formulations used on polar solvent fires.
The novel perfluoroalkyl-substituted polyamino acid of the present invention comprises an oligomer or copolymer of an aliphatic diamino carboxylic acid having 3 to 10 carbon atoms and containing at least two perfluoroalkyl groups attached to nitrogen atoms through a linking group.
More particularly, the perfluoroalkyl-substituted polyamino acid comprises an oligomer or polymer of an aliphatic diamino carboxylic acid having 3 to 10 carbon atoms and containing at least two structural units, J, having perfluoroalkyl groups, RF, attached to nitrogen atoms of the oligomer or copolymer through a linking group L,
wherein
J is a mixture of 
L is xe2x80x94Qxe2x80x94CH2xe2x80x94CHxe2x95x90CHxe2x80x94 and/or xe2x80x94Qxe2x80x94CH2xe2x80x94CHIxe2x80x94CH2xe2x80x94, in which
Q is CH2xe2x80x94CHOHxe2x80x94CH2O, (Cxe2x95x90S)xe2x80x94NH or a direct bond,
RF is a monovalent perfluorinated alkyl or alkenyl group,
R is hydrogen or an ionic or nonionic water-solubilizing group,
m is an integer from 1 to 8 and
n is an integer from 2 to 100.
Preferably Q is xe2x80x94CH2xe2x80x94CHOHxe2x80x94CH2xe2x80x94Oxe2x80x94 or a direct bond. It is most preferably xe2x80x94CH2xe2x80x94CHOHxe2x80x94CH2xe2x80x94Oxe2x80x94.
Each RF is independently a monovalent perfluorinated alkyl or alkenyl, linear or branched organic radical having four to twenty fully fluorinated carbon atoms. Preferably RF is saturated and contains 6-12 carbon atoms, is fully fluorinated and contains at least one terminal perfluommethyl group. Most preferably RF is a xe2x80x94C6F13 group.
R is preferably hydrogen. When R is an ionic water-solubilizing group, it is preferably a carboxy-, phosphate-, sulfate- sulfonate- or quaternary ammonium-containing group. When R is a nonionic water-solubilizing group, it is preferably an amide-, tertiary amino- or poly-(oxyethylene)-containing group.
The number of methylene repeating units, m, is preferably 1-5. Most preferably m is 4.
Advantageously the novel oligomer or copolymer has a weight average molecular weight of from about 500 to 100,000 as determined by conventional techniques such as gel permeation chromatography.
The perfluoroalkyl-substituted polyamino acids of the present invention are reaction products of (A) an aliphatic diamino acid having 3 to 10 carbon atoms, (B) an amino-reactive chain extender such as epichlorohydrin, a dihalide or a diepoxide, (C) allyl glycidyl ether, allyl chloride or bromide, or allyl isothiocyanate and (D) a perfluoroalkyl iodide, and, optionally (E) an amino acid other than (A), a monoglycidyl compound other than allyl glycidyl ether or an aliphatic or aromatic amine or diamine, and also, optionally, (F) an amino-reactive organic or inorganic compound selected from halogenated carboxylic- or sulfonic acids or their salts, vinyl unsaturated acids, anhydrides and glycidol and chloroacetamide.
Suitable aliphatic diamino acid starting materials for use in the present invention have 2 primary amino groups attached to a carboxylic acid-containing radical containing 3 to 10 carbon atoms, which radical can be linear or branched. Preferably it is linear. Advantageously the amino groups are at the ends of a linear chain with a carboxylic acid radical and an amino radical bonded to the same carbon atom. Thus, most preferably the diamino acid is of the formula 
where m is an integer from 1 to 8. The number of methylene repeating units, m, is preferably 1-5. Most preferably m is 4. Preferred diamino acids include 2,3-diaminopropionic acid, 2,4-diaminobutyric acid, 2,5-diaminopentanoic acid (omithine), 2,6diaminohexanoic acid (lysine) and 2,7-diaminoheptanoic acid. Especially preferred are 2,5diaminopentanoic acid (omithine) and 2,6-diaminohexanoic acid (lysine), with lysine being most especially preferred.
Omithine and lysine are naturally occurring readily available amino acids. Other suitable aliphatic diamino acid starting materials are either known per se or can be made by known methods.
Preferred compounds (B) are epichlorohydrin, 1,2-dichloroethane, 1,4-dichlorobutane, 1,3-dichloro-2-hydroxypropane, xcex1,xcex1xe2x80x2-dichloro-p-xylene, butanediol digylcidyl ether and N,N-digylcidylaniline, with epichlorohydrin being especially preferred.
Preferred compound (C) is allyl glycidyl ether.
Preferred compounds (E) are glycine, glucosamine and glycidyl trimethylammonium chloride, with glycidyl trimethylammonium chloride being most preferred.
Preferred compounds (F) are halogenated acids such as chloroacetic acid, chloropropionic acid and chlorosulfonic acid and their salts, unsaturated acids such as acrylic acid, itaconic acid, vinyl sulfonic acid and vinyl phosphonic acid, 2-acrylamido-2-methylpropane sulfonic acid and 2-acrylamido glycolic acid, anhydrides such as maleic-, succinic- phthalic- and acetic anhydrides and sodium meta-triphosphate. Most preferred are chloroacetic acid, chloroacetamide and sodium meta-triphosphate.
The novel compounds are the reaction products of (A), (B), (C), (D), (E) and (F) which are preferably reacted in molar ratios of
(A) 1/(B)0.2-0.99/(C)0.15-0.6/(D)0.15-0.5/(E)0-0.2/(F)0-0.2.
Especially preferred compounds are the reaction products wherein the molar ratios are
(A)1/(B)0.6-0.95/(C)0.25-0.4/(D)0.2-0.35/(E)0-0.1/(F)0-0.1, wherein (E) is glycine or glycidyl trimethylammonium chloride and (F) is chloroacetic acid, chloroacetamide or sodium-trimetaphosphate.
The most preferred compounds are the reaction products wherein the molar ratios are
(A)1/(B)0.7-0.95/(C)0.27-0.33/(D)0.25-0.3.
The novel perfluoroalkyl-substituted polyamino acids of this invention are preferably obtained by first reacting an aliphatic diamino acid having 3 to 10 carbon atoms with an amino-reactive chain extender, for example epichlorohydrin, a dihalide or an aliphatic diepoxide, in the presence of an acid acceptor, secondly reacting the intermediate polyamino acid with an amino-reactive allyl compound which is preferably selected from the group consisting of allyl glycidyl ether (AGE), allyl chloride or allyl bromide or with allyl isothiocyanate, then reacting the polyallyl-substituted polyamino acid with a perfluoroalkyl iodide in the presence of a free radical initiator such as an azo compound or peroxide at an appropriate initiation temperature, preferably at temperatures of between 50 and 80xc2x0 C. Sodium metabisulfite is preferably present during this step to reduce iodine. Alternatively, one can first react the aliphatic diamino acid having 3 to 10 carbon atoms with an amino-reactive allyl compound such as allyl glycidyl ether; then react this product with a perfluoroalkyl iodide and finally react this product with the chain-extending epichlorohydrin, dihalide or diepoxide. However the properties of the resulting perfluoroalkyl-substituted polyamino acids differ somewhat from those prepared by the first route.
The addition of a perfluoroalkyl iodide to an allyl compound may be carried out according to the process described in U.S. Pat. No. 5,585,517. Solvents can be present, for example ketones such as acetone, methyl ethyl ketone or methyl propyl ketone or alcohols such as ethanol, propanol or butanol. If a solvent is used, it is preferably distilled off before dilution of the reaction mixture with water. The reaction is typically carried out over 4 to 10 hours at 50-80xc2x0 C. with good agitation. Any remaining amino groups can be further reacted with suitable reagents (E) or (F), either before or after addition of the perfluoroalkyl iodide, to introduce functional groups such as additional acid or amino groups.
Due to the basic nature of the reaction medium, much of the organic iodide is eliminated during the course of the reaction of the perfluoroalkyl iodide. The product obtained is therefore a mixture of halogenated and dehydrohalogenated species. If complete dehydrohalogenation is desired, the addition of a strong inorganic base such as sodium or potassium hydroxide or a strong organic base such as 1,8-diazabicyclo(5.4.0)-undec-7-ene (DBU) is necessary.
It has further been found that the addition of a periluoroalkyl iodide to an allyloxy group can be carried out using catalytic amounts of sodium dithionite at temperatures between 0 and 200xc2x0 C., as disclosed in copending U.S. patent application Ser. No. 60/084,815. An advantage of this process is that less color is produced and the process can be carried out at higher aqueous dilutions.
The final product mixture is then diluted, if desired, with sufficient deionized water to adjust the solids content to 15 to 50% and the fluorine c ontent to 4 to 10%. Thus another aspect of the present invention is an essentially aqueous solution comprising 15 to 50% of an oligomer or copolymer of an aliphatic diamino acid having 3 to 10 carbon atoms and containing at least two perfluoroalkyl groups attached to nitrogen atoms through a linking group. This aqueous solution is useful in the preparation of foam stabilizers and for treating paper.
When the compounds of this invention are used to improve the oil repellency of paper, they are applied to the paper or paper board as an external coating by any conventional method, such as padding or spraying, or in a size press in amounts to deposit from 0.02 to 0.5% fluorine by weight on the paper. In addition to the fluorochemical, an y of the conventional binders used in the paper industryxe2x80x94such as polymeric latex binders, caboxymethyl cellulose and polyvinyl alcoholxe2x80x94and sizing agents, such as ionic and nonionic starches such as ethoxylated and oxidized starches, and water sizing agents such as alkyl ketene dimer (AKD) or alkylsuccinic anhydride (ASA) can be employed.
In the following examples, external sizing application was accomplished using the following procedure: the products were applied to 34# watedeaf paper stock using a Wemer Mathis laboratory padder in the horizontal mode. Samples were co-applied with 2% Penford 280 starch as sizing agent and Chel(copyright) DPTA 41 (from Ciba Specialty Chemicals Corp.) as a chelating agent in the standard manner. The paper was dried for 30 seconds on each side at 100xc2x0 C. using a photographic drier.
The oil repellency of a surface is determined by using the TAPPI UM 557 OIL KIT TEST. This test method consists of applying twelve different mixtures of castor oil/heptane/toluene having a surface tension range from 34.5 to 22.0 dynes/cm. The rating is based on penetration that occurs within 15 seconds of application; the ratings go from 1 (lowest), to 12.
As taught in column 2 of U.S. Pat. No. 5,496,475, the teachings of which are incorporated by reference, AFFF and AR-AFFF agents are generally sold in the form of liquid concentrates. These concentrates, which are rather complex mixtures (see column 7, lines 9-36), are diluted with fresh or salt water in proportioning equipment and sprayed onto a burning liquid as a foam.
The agents are usually sold as so-called xe2x80x9c3xc3x976xe2x80x9d and xe2x80x9c3xc3x973xe2x80x9d AR-AFFF concentrates, with the trend in the industry being toward the latter, where the numbers indicate the percent by weight of the concentrate contained in the diluted formulation for a fighting a fire involving a nonpolar fuel such as gasoline and a polar fuel, respectively. Thus a xe2x80x9c3xc3x973xe2x80x9d AR-AFFF concentrate can be employed at the 3 percent level to combat a fire involving either a nonpolar or a polar fuel.
When the inventive compounds are used as a foam stabilizer in an AR-AFFF agent, they are added to conventional AFFF and AR-AFFF formulations. The performance of an AR-AFFF formulation can be improved by replacing, entirely or in part, a conventional foam stabilizer by at least one inventive compound. In addition a conventional AFFF formulation can be converted into an AR-AFFF agent by incorporating an effective amount of an inventive compound therein.
The amount of the foam stabilizer typically used in 3xc3x973 AR-AFFF agents ranges from 1% to 3% by weight of the active ingredients. From 10 up to about 40% of the fluorine of the final formulation is thus derived from the foam stabilizer.
The novel foam stabilizers of this invention exhibit superior performance when compared to products of the prior art, especially on hot acetone.
In order to test the efficacy of the novel foam stabilizers, the following basic AR-AFFF formulation, free of any foam stabilizer, was used:
This mixture is referred to in the examples as AR-AFFF base.
Measurements of Foam Expansion Ratio (FXR) and Quarter Drain Time (QDT) were performed using the following procedure. A 3% solution of AR-AFFF was prepared in sea or tap water. The test solution was drawn into the calibrated liquid container by vacuum. The volume of the test solution was adjusted to 100 ml. The test solution was pressurized to 40 psig with compressed nitrogen. Compressed air was turned on and adjusted to 33 psig. The test solution was mixed with air at the mixing port before foaming at the nozzle. The volume of foam was measured in a 1000 ml. graduated cylinder. The Foam Expansion Ratio of the foam was determined as the ratio of the total foam volume to the volume of the original test solution. Quarter Drain Time was measured as the time it took to collect 25 ml. of drained liquid (=one quarter of the test solution) from the foam. Each test measurement was duplicated and the average was reported.
Foam Life on hot 2-propanol was measured using the following procedure. A 3% solution of AR-AFFF was prepared in sea or tap water. The test solution was loaded in the calibrated liquid container by using vacuum. The volume of the test solution was adjusted to 75 ml. The test solution was pressurized to 40 psig with compressed nitrogen. Compressed air was turned on at 33 psig. The test solution was mixed with air at the mixing port before foaming at the nozzle. To a glass Pyrex pan 6.5 inchesxc3x9710 inches was added 250 ml. of 2-propanol at 70xc2x0 C. The test solution was discharged as foam onto the hot 2-propanol and formed a blanket completely covering its surface. Foam Life was measured as the time it took for 50% of the foam area to collapse. Each test measurement was duplicated and the average was reported.
Analytical Methods
Progress of the reaction of allyl glycidyl ether with the lysine derivative was followed by gas chromatography. The reaction was allowed to continue until allyl glycidyl ether was no longer detected.
ZONYL(copyright) TELA-L consumption was also followed by gas chromatography using an HP 5890 GC with FID detector and a Supelco SPB-1, 60 mesh/0.53 mm by 3.0 m column.
Determination of Ionic Chloride and Iodide was done by titration as described below: Equipment: Brinkmann Auto Titrator, Model E438; Fisher Ag/AgCl Reference Electrode; Fisher Silver Billet Indicating Electrode; Aldrich Standard AgCl. Procedure: 1) Weigh about a 0.2 g sample for chloride or 1.0 g for iodide into a 200 ml beaker and dilute with 150 ml of water and add 1 ml of glacial acetic acid. 2) Titrate with 0.1023 M AgNO3 at 750 mv and a speed of xe2x80x9c2xe2x80x9d.       Calculation:              %      ⁢              xe2x80x83            ⁢      Conversion      ⁢              xe2x80x83            ⁢              (                  based          ⁢                      xe2x80x83                    ⁢          on          ⁢                      xe2x80x83                    ⁢                      Cl            -                          )              =                  ml        xc3x97        M        xc3x97                  (                      Total            ⁢                          xe2x80x83                        ⁢            Rxn            ⁢                          xe2x80x83                        ⁢            Mass                    )                xc3x97        100        ⁢        %                              (                      g            ⁢                          xe2x80x83                        ⁢            sample                    )                ⁢                  (                      mmol            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            Chloroacetic            ⁢                          xe2x80x83                        ⁢            acid                    )                                %      ⁢              xe2x80x83            ⁢      Conversion      ⁢              xe2x80x83            ⁢              (                  based          ⁢                      xe2x80x83                    ⁢          on          ⁢                      xe2x80x83                    ⁢                      I            -                          )              =                  ml        xc3x97        M        xc3x97                  (                      Total            ⁢                          xe2x80x83                        ⁢            Rxn            ⁢                          xe2x80x83                        ⁢            Mass                    )                xc3x97        100        ⁢        %                              (                      g            ⁢                          xe2x80x83                        ⁢            sample                    )                ⁢                  (                      mmol            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢                          R              F                        ⁢            I                    )                    